1. Field of the Invention
The present invention relates to a lens used in an optical pickup device or the like which performs an operation of reading out signals recorded in an optical disc by laser light, a method for mounting the lens on a mounting portion, and an optical pickup device incorporated with the lens.
2. Disclosure of Related Art
An optical disc apparatus which applies laser light emitted from an optical pickup device to a signal recording layer of an optical disc to perform an operation of reading out signals recorded in the optical disc and an operation of recording signals into the optical disc has been widely used. As such an optical disc apparatus, an apparatus using an optical disc called CD (Compact Disc) or DVD (Digital Versatile Disc) is widely known in general. Further, an optical disc apparatus using an optical disc with improved recording density, i.e., a Blu-ray standard optical disc has been developed in these days.
An optical pickup device is configured to condense laser light emitted from a laser diode onto a signal recording layer of an optical disc by a light-condensing function of an objective lens. In the optical pickup device, a photodetector is irradiated with laser light reflected from the signal recording layer. The photodetector is provided with a sensor such as a quadrant sensor. A focus error signal and a tracking error signal are generated from signals obtained from changes in light amount and position of the laser light applied to the quadrant sensor. By controlling a position of the objective lens using the focus error signal and the tracking error signal, the operation of reading out a signal recorded in the optical disc or the like is performed.
An objective lens provided in an optical pickup device is fixedly attached by an adhesive to a lens holder supported by a support member such as four support wires so that the objective lens can perform a displacement operation (a focus control operation) in a direction perpendicular to the signal plane of the optical disc and a displacement operation (a tracking control operation) in a radial direction of the optical disc.
It is necessary to configure the optical pickup device in such a manner that the angle of an optical axis of the objective lens becomes optimum with respect to a signal plane of the optical disc so as to perform the focus control operation and the tracking control operation accurately. Such an angle adjustment operation for the objective lens can be performed with e.g. an auto collimator device.
The angle adjustment operation is performed after a UV curable adhesive has been applied between the objective lens and the lens holder. Specifically, the angle adjustment operation is performed in a state that the adhesive has not been cured, i.e., UV light has not been irradiated. When the mounted angle of the objective lens is adjusted to be an optimum angle by the angle adjustment operation, the UV light is irradiated to cure the adhesive.
In the case where such an application work of the adhesive is performed by hands, there may be a variation in application amount and position of the adhesive. If there is a variation in application amount and position of the adhesive, there may occur problems in an oscillation characteristic and reliability of the optical pickup device. In view of the above, the adhesive application work must be performed exactly.
Since visual inspection by workers is conducted for judgment and confirmation on whether an exact application work of the adhesive is performed or not, there is a problem that technical sophistication and confirming ability of workers may influence quality of the optical pickup device.